A chemically amplified positive resist composition is used for semiconductor microfabrication.
In semiconductor microfabrication, especially, in liquid immersion lithography process, it is desirable to suppress the formation of defect.
It has been known that one of big problems in liquid immersion lithography process is defect caused by residual fluid droplets on the resist film (e.g. C. V. Peski et al., “Film pulling and meniscus instability as a cause of residual fluid droplets”, Presentation at the 2nd International Symposium on Immersion Lithography, September, 2005, and D. Gil et al., “The Role of Evaporation in Defect Formation in Immersion Lithography”, Presentation at the 2nd International Symposium on Immersion Lithography, September, 2005). The said defect is the specific one in liquid immersion lithography and the defect is formed by conducting post-exposure baking of the resist film on which fluid droplets was remained.
It has been known that number of the defect caused by residual fluid droplets on the resist film is associated with the receding contact angle of the resist film and it is possible to suppress the formation of the defect caused by residual fluid droplets on the resist film by using the resist composition forming the resist film having higher receding contact angle.
JP 2005-266767 A discloses a positive resist composition for immersion exposure containing an acid generator and a resin comprising a structural unit represented by the formula:
and a structural unit derived from a methacrylate monomer having no fluorine atom, and the resist film derived from the resist composition has 50 to 700° of the contact angle. However, the resist film having higher receding contact angle is not disclosed in JP 2005-266767A and it is desirable to develop a resist composition forming the resist film having higher receding contact angle.